THE ALGiE 



219 



SPIROGYRA, — ONE OF THE CONJUGATING ALG^ 



278. Occurrence. — Sinrogyra, one of the commonest of 

 the plants known as pond-scums, occurs widely distributed 

 throughout the country in ponds, springs, and clear, slow 

 streams. It is of a bright green 

 color (yellowish green when 

 producing spores). In warm 

 sunny weather the masses usu- 

 ally float, buoyed up by the 



Fig. 153. A Group of Diatoms. 



A, Achnanth.es; B, Cocconetna; C, ileriil- 

 ion; D, Pleurosigma. 



Fig. 154. A Group of Desmids. 



A, Micrasterias ; B, B', Staurastrum 

 (two views) ; C, Closterium. 



numerous oxygen bubbles which the plants set free. It 

 grows in unfrozen springs even in midwinter. Not in- 

 frequently several species are found growing with the 

 filaments intermixed. 



